Testing of telephone lines

ABSTRACT

A telephone line testing device for use with a PABX having a plurality of input lines. The testing device includes test circuitry, a first connecting means for connection to a telephone line of a telephone system, a second connecting means for connection to a desired input line of the PABX, a first switch means for connecting either the PABX input line or the test circuitry to the telephone line. The test circuitry includes a test signal generating means for generating a test signal, a ringing signal detection means for detecting the presence of a ringing signal on the telephone line, and a second switch means which is responsive to the ringing signal detection means for automatically supplying a test signal generated by the test signal generating means to the telephone system when the test circuitry is connected to the telephone line by the first switch means and a ringing signal is desired.

This invention relates to a telephone line testing device for use with aPABX.

U.S. Pat. No. 3,898,396 provides test equipment for verifying trunkrouting in a telephone system. A series of spoken words is provided toidentify the area code and the telephone exchange to which a trunk undertest is connected. The equipment includes a plurality of input channelseach coupled to a verification line for a corresponding telephoneexchange. A ringing signal on any channel is detected and special logiccircuitry is provided to identify the required telephone exchange digitsand to produce a read out of the area code and exchange digits for thatchannel.

With PABX's there is always a difficulty in identifying if a problem isthe responsibility of the organisation that supplied and services thePABX and its associated wiring, or of the utility supplying thetelephone lines. The present invention provides a solution thereto.

According to the invention there is provided a telephone line testingdevice for use with a PABX having a plurality of input lines connectedto a plurality of telephone lines of a telephone system, each of thePABX input lines being associated with a telephone line, which includes

test circuitry having

a test signal generator for generating a test signal;

a ringing detector for detecting the presence of a ringing signal on atelephone line; and

a second switch means which is responsive to the ringing signal detectorfor automatically supplying a test signal generated by the test signalgenerator when a ringing signal is detected;

a first connecting means for connection to the telephone lines of thetelephone system;

characterised therein that it further includes

a second connecting means for connection to the input lines of the PABX;

a first switch means for connecting a selected one of the telephonelines either to the PABX input line associated with that telephone lineor the test circuitry.

It will be appreciated by those skilled in the art that the test signalgenerator may be connected directly to the first switch means and maythen be energised by the second switch means when a ringing signal isdetected, or it may be connected to the first switch means via thesecond switch means. It the test signal generator is connected directlyto the first switch means it may have a sufficiently high impedance sothat the telephone line is not closed when the first switch means isoperated.

The first connecting means may include a plurality of first terminals towhich a corresponding number of telephone lines may be connected.

The second connecting means may also include a plurality of secondterminals to which a corresponding number of PABX input lines may beconnected, there being the same number of second terminals as there arefirst terminals, and with designed first and second terminals beingassociated with one another.

The first switch means may include a plurality of mechanically operableswitches, each switch having a first contact connected to an associatedfirst terminal, a second contact connected to the second terminalassociated with said first terminal, a third contact connected to thetest circuitry, and a contactor for connecting the first contact toeither the second or third contact.

The ringing signal detector may be connected to all the third contactsof the first switch means.

The test signal generator may be connected to all the third contacts ofthe first switch means via the second switch means.

The telephone line to be tested may be accessed via the PABX, usinganother telephone line.

By means of the invention a PABX telephone operator may, if there is afault on one of the lines, determine easily and quickly if the fault isin the telephone line or in the PABX.

The invention is now described, by way of an example, with reference tothe accompanying drawings, in which:

The telephone testing device may have a lighting protection means.

The telephone line to be tested may be accessed via the PABX, usinganother telephone line.

By means of the invention a PABX telephone operator may, if he believesthat one of the telephone lines is faulty, easily and quickly identifywhich telephone line it is.

The invention is now described, by way of an example, with reference tothe accompany drawings, in which:

FIG. 1 shows a schematic circuit diagram of a telephone line testingdevice in accordance with the invention connected to a PABX and atelephone line;

FIG. 2 shows schematically how the telephone testing device is connectedto a plurality of telephone lines; and

FIG. 3 shows a schematic circuit diagram of a second embodiment of testcircuitry.

Referring now to FIG. 1, a telephone line testing device in accordancewith the invention is generally indicated by reference numeral 10. Thetelephone line testing device 10 includes test circuitry 13, a firstconnecting means 14 for connection to a telephone line 12 of a telephonesystem, a second connecting means 15 for connection to an input line 16of a PABX 17, a third connecting means 18 for connection to the testcircuitry 13, and a first switch 19 for connecting either the PABX line16 or the test circuitry 13 to the telephone line 12. The connectingmeans 14, 15 and 18 are in the form of sets of terminals 20.1 and 20.2,21.1 and 21.2, and 22.1 and 22.2, respectively. The first switch 19 hascontacts 25.1 and 25.2, 27.1 and 27.2, and 29.1 and 29.2 and contactors31.1 and 31.2, such that the first switch 19 is a double pole typeswitch. The contactors 31.1 and 31.2 are manually operated and connecteither the contacts 25.1 and 25.2 to the contacts 27.1 and 27.2respectively or to the contacts 29.1 and 29.2 respectively. Asindicated, the terminals 20.1 and 20.2 are connected to the contacts25.1 and 25.2 respectively; the terminals 21.1 and 21.2 are connected tothe contacts 27.1 and 27.2 respectively; and the terminals 22.1 and 22.2are connected to the contacts 29.1 and 29.2 respectively.

The test circuitry 13 has a test signal generator 26 provided with anactivation switch 38; a ringing signal detector 28 for detecting thepresence of a ringing signal on the telephone line 12; and a secondswitch 30 which is responsive to the ringing signal detector 28 forautomatically connecting the test circuitry 13 to the telephone systemwhen the test circuitry 13 is connected to the telephone line 12 by theswitch 19 and a ringing signal is detected. The test signal generator 26generates a suitable audible signal.

The test circuitry 13 includes a DC blocking capacitor 32, a rectifyingbridge 34 and a storage capacitor 36. The second switch 30 is in theform of a relay, having a coil 30.1 and normally open contactors 30.2and 30.3. The contactor 30.2 bypasses the blocking capacitor 32 when aringing signal is detected. The contactor 30.3 connects the test signalgenerator 26 to the telephone line 12. The rectifying bridge 34 has twoLED's 34.1 and 34.2.

As seen in FIG. 1, the telephone line 12 has two cores 33.1 and 33.2.Similarly, the PABX line 16 has two cores 35.1 and 35.2. The cores 33.1and 33.2 are connected to the terminals 20.1 and 20.2 respectively. Thecores 25.1 and 35.2 are connected to the terminals 21.1 and 22.2respectively. The test circuitry 13 is connected to terminals 22.1 and22.2 by a two core wire having cores 23.1 and 23.2.

The rectifier bridge 34 is connected to terminals 22.1 and 22.2 via theblocking capacitor 32. The test signal generator 26 is also connected toterminals 22.1 and 22.2 via the second switch 30.

The method for determining whether there is a fault in the telephoneline 12 upstream from the PABX 17 includes operating the first switch 19to disconnect the telephone line 12 from the PABX 17 and connect thetelephone line 12 with the test circuitry 13. The telephone line 12 isdialed by an operator using the PABX 17 or some other telephoneinstrument. If the line 12 is functional, the alternating current causedby the ringing tone is converted to a direct current by the rectifierbridge 34 causing the relay 30 to close the telephone line 12 andconnect the operator's telephone to the test signal generator 26 whichprovides an audible signal which is heard by the operator. In addition,when relay 30 closes, the contactor 30.2 bypasses the blocking capacitor32 causing the LED 34.1 or 34.2 to indicate a direct current. If thetelephone line 12 is not functional the test signal is not heard and/orthe LED's 34.1 and 34.2 are not energised. If the test signal is heardand/or LED 34.1 or 34.2 emits light then the fault originates at thePABX 17 and if no test signal is heard or not light emitted by LED 34.1or 34.2 then the fault originates from the telephone line 12.

Referring now to FIG. 2, a multiple switch system in accordance with theinvention is generally indicated by the reference numeral 40. Themultiple switch system comprises a number of switches 19.1, 19.2 to 19.Nwhich are connected to a corresponding number of telephone lines 12.1,12.2 and 12.N and PABX lines 16.1, 16.2 and 16.N. Each switch 19.1, 19.2to 19.N is as shown in FIG. 1, with each telephone line 12.1, 12.2 to12.N having two cores connected to the terminals 20.1 and 20.2 of itsassociated switch and each PABX line 16.1, 16.2 to 16.N having two coresconnected to the terminals 21.1 and 21.2 of its associated switch. Thetest circuit 13 is connected to the terminals 22.1 and 22.2 of all theswitches 19. Any one of the telephone lines 12.1, 12.2 to 12.N can beconnected to the test circuitry 13 to enable an operator to test thatparticular line.

Referring now to FIG. 3, a second embodiment of test circuitry 13.1 isshown. This embodiment 13.1 has cores 23.1 and 23.2 which are connectedto the terminals 22.1 and 22.2. It further has an IC test signalgenerator 26.1 which is connected to the cores 23.1 and 23.2 by means ofa full wave rectifier 34, a transformer 54, and SCR switch 56 and asignal capacitor 58. It also has a ringing signal detector 28.1 alsoconnected to the cores 23.1 and 23.2. This ringing signal detectorcomprises a half wave rectifier 60, a charging capacitor 62 and an optocoupler 64 which is connected to the gate of the SCR 56. In use, whenthe test circuitry 13.1 is connected to an operative telephone line, andan AC ringing signal is received, it is rectified by the rectifier 60,the capacitor 62 charges and the opto coupler 64 triggers the SCR 56.When the SCR 56 is switched on it supplies power to the IC 26.1 and theaudible test signal is then supplied to the telephone line. When theline is disconnected, the test circuitry is deenergised and reset.

I claim:
 1. A telephone line testing device for use with a PABX having aplurality of input lines connected to a plurality of telephone lines ofa telephone system, each of said input lines of the PABX beingassociated with one of said telephone lines, said telephone line testingdevice including: (a) test circuitry having (i) a signal generator forgenerating a test signal; (ii) a ringing signal detector for detectingthe presence of a ringing signal on said telephone lines; and (iii) asecond switch means which is responsive to the ringing signal detectorfor automatically supplying a test signal generated by the signalgenerator when a ringing signal is detected on one of said telephonelines; (b) a first connecting means for connection to said telephonelines of the telephone system; (c) a second connecting means forconnection to said input lines of the PABX; and (d) a first switch meansfor connecting a selected one of said telephone lines either to saidinput line of the PABX associated with said selected one of saidtelephone lines or the test circuitry.
 2. The telephone line testingdevice, as claimed in claim 1, wherein the first connecting meansincludes a plurality of first terminals to which a corresponding numberof said telephone lines may be connected.
 3. The telephone line testingdevice, as claimed in claim 2, wherein the second connecting meansincludes a plurality of second terminals to which a corresponding numberof said input lines of the PABX may be connected, there being the samenumber of said second terminals as there are said first terminals, andwith designated ones of said first and said second terminals beingassociated with one another.
 4. The telephone line testing device, asclaimed in claim 3, wherein the first switch means includes a pluralityof mechanically operable switches, each of said mechanically operableswitches having a first contact connected to an associated one of saidfirst terminals, a second contact connected to said second terminalassociated with said first terminal, a third contact connected to thetest circuitry, and a contactor for connecting the first contact toeither the second contact or the third contact.
 5. The telephone linetesting device, as claimed in claim 4, wherein the ringing signaldetector is connected to all the third contacts of the first switchmeans.
 6. The telephone line testing device, as claimed in claim 5,wherein the signal generator is connected to all the third contacts ofthe first switch means via the second switch means.